Quantum computing will challenge today’s crypto and blockchain, but it also makes space for stronger, future-proof solutions. However, preparation is key and must start now, says Filippo Marcuccini, data scientist at Sopra Steria Italy.
Try to imagine a type of computer that does not follow the traditional rules of binary logic. A machine capable of existing in multiple states simultaneously, whose operation is governed by counterintuitive yet rigorous physical laws: those of quantum mechanics.
The history of computing has always been marked by a series of revolutions. From the first electronic computers as large as entire rooms and relying on vacuum tubes and punched cards to modern smartphones, our idea of a computer has remained tied to a fundamental concept: machines that operate in binary mode through an ordered sequence of zeros and ones.
It is on this foundation that Alan Turing, in the 1930s, conceived the theoretical model of the machine that bears his name, the cornerstone of modern computer science. That model was based on deterministic and sequential logic, with each operation following another according to precise and predictable rules. The first real computers adhered to this principle. Each bit was either on or off, with no intermediate states.
However, quantum computing introduces a completely new paradigm. Instead of being limited to one state at a time, quantum bits or qubits can exist in a superposition of states, simultaneously assuming the value of zero and one. This phenomenon, along with other properties such as entanglement and interference, opens the door to a new form of computation capable of solving problems that are unsolvable even for the most powerful traditional supercomputers.
In this context, the quantum revolution does not merely represent a technological improvement, but a radical transformation of our way of conceiving information and data processing.
The emergence of the qubit
In the world’s most advanced laboratories, physicists and computer scientists are developing a new generation of computers based on qubits, quantum units of information that challenge classical logic. Unlike traditional bits, which can only be 0 or 1, a qubit can exist in both states simultaneously, a property called superposition.
Imagine a coin spinning in the air. While in flight it is neither heads nor tails, but a combination of both possibilities. Only when the coin lands does this superposition collapse into a defined outcome.
Similarly, a qubit can simultaneously represent different percentages of 0 and 1 until it is measured. Mathematically, the state of a qubit can be described as: |mix 0 and 1⟩ = α|0⟩ + β|1⟩, where α and β determine the probabilities of measuring the qubit in one of the two base states.
This revolutionary feature allows quantum computers to process information in ways that are impossible for classical computers, opening up unimaginable possibilities while also posing threats to current security systems.
With great power comes great responsibility
To explain the real revolution, imagine an extremely complex maze with thousands of possible paths. A classical computer must explore each path sequentially, taking a long time to find the exit. A quantum computer can explore all paths simultaneously, reaching the solution almost instantly.
A traditional computer (Classical Physics) would have to explore every single path sequentially, taking a long time to find the exit. A quantum computer (Quantum Physics), on the other hand, can explore all paths simultaneously, each with a certain probability, reaching the solution in a fraction of a second.
Figure 1: Representation of a maze with point A at the top indicating the entrance, and point B at the bottom corresponding to the exit.
This capability has disruptive implications for sectors like cryptocurrencies and blockchain. The blockchains of Bitcoin, Ethereum, and other cryptocurrencies rely on a fundamental principle – cryptographic algorithms so complex that it is virtually impossible to break them using today’s computers.
The private keys protecting digital wallets are generated through extremely complex mathematical calculations, and breaking these algorithms with classical computers would take thousands of years of continuous computation. Thanks to its structure, blockchain reduces the need for intermediaries (like banks or institutions) and increases transparency, security, and reliability in digital systems.
The quantum threat to security systems
But how exactly do quantum computers threaten blockchains and cryptocurrencies? The issue lies in the vulnerability of current cryptographic systems. Blockchain security relies mainly on public key cryptography, a system that uses mathematically linked key pairs – a public key (visible to everyone) and a private key (known only to the owner).p>
The strength of these systems is based on the difficulty of solving certain mathematical problems, such as factoring very large prime numbers. To give a concrete example, imagine a digital lock that protects your Bitcoin wallet. This lock is virtually unbreakable by classical computers, as it would require thousands of years of computation. However, a quantum computer could open it in just a few minutes, thanks to its ability to explore countless possibilities simultaneously.
Particularly vulnerable is the ECDSA (Elliptic Curve Digital Signature Algorithm), used by Bitcoin and many other cryptocurrencies. Simply put, ECDSA leverages the mathematical properties of elliptic curves, complex geometric shapes described by specific equations, to generate digital signatures that verify the authenticity of transactions.
When Bitcoin is sent, the wallet creates a unique digital signature using the private key, confirming the legitimate owner as the one authorised to spend those funds. A surprising fact, researchers estimate that a quantum computer with just 4,000 stable qubits could break Bitcoin’s ECDSA algorithm in under an hour, successfully deriving private keys from exposed public keys. According to a study by Cornell University, about 25% of all circulating Bitcoin may be particularly at risk due to address reuse practices that expose public keys.
Although today’s quantum hardware is still far from that level of power (the most advanced quantum computers currently operate with a few hundred qubits, and suffer from high error rates), progress in this field is rapid. Several companies, including IBM, have already released ambitious roadmaps for developing increasingly powerful quantum processors over the coming years.
Cybersecurity experts estimate a 50% chance that quantum computers will be able to break current cryptographic systems by 2031. Even now, global public funding for quantum research is rising significantly (+37% compared to 2023), with Asia leading the way ($22.1 billion), followed by Europe ($12.9 billion) and America ($6 billion).
However, the European approach is more fragmented compared to other regions, with only 11% of funding coming directly from the European Union. Tech giants such as Google and IBM are already developing increasingly powerful quantum processors. This paradigm shift could render current digital security mechanisms obsolete, necessitating a complete reinvention of the security protocols on which the global digital economy is built.
Post-quantum cryptography: A new digital shield
The quantum revolution has raised serious concerns among cybersecurity experts. Current cryptographic systems, which today protect the confidentiality of our communications, could become vulnerable to the power of future quantum computers.
In response to this challenge, Post-Quantum Cryptography (PQC) has emerged a field dedicated to designing algorithms resistant to quantum attacks. The term "post-quantum" reflects the need to prepare for an era in which classical cryptography will no longer be sufficient to guarantee security.
In this context, the National Institute of Standards and Technology (NIST) has identified several particularly promising projects, explained in more detail below, including Kyber, a lattice-based algorithm for secure key exchange, and Dilithium, designed for secure and efficient digital signatures. Other noteworthy strategies include McEliece, based on error-correcting codes, and SPHINCS+, a digital signature scheme relying solely on hash functions.
Lattice-based cryptography, the foundation of Kyber, uses complex mathematical structures known as lattices. Imagine a multi-dimensional grid where finding a specific point becomes increasingly difficult as the dimensions grow. This complexity poses a formidable challenge even for quantum computers. Kyber leverages this principle to generate encryption keys that allow two parties to communicate securely.
Dilithium, also based on lattices, functions like an unforgeable digital seal. When we sign a digital document with Dilithium, we create a mathematical proof of our identity so intricate that not even a quantum computer can replicate it. It’s like having a personal stamp with such an elaborate design that no technology in the world could perfectly duplicate it. Beyond these, other families of algorithms are gaining traction.
Error-correcting codes, such as the McEliece system, were originally developed to ensure reliable data transmission even in the presence of interference. They work by deliberately introducing “noise” into the message – noise that only the intended recipient knows how to filter. It’s like sending a message in a foreign language where only the recipient holds the dictionary to translate it.
Hash-based signatures, like SPHINCS+, operate on a different principle. A hash function is like a one-way paper shredder – it’s easy to feed in a document, but impossible to reconstruct it from the shredded pieces. SPHINCS+ generates digital signatures so complex that even quantum computers cannot reverse-engineer them to forge documents.
Developers can further enhance protection by combining quantum-resistant algorithms with classical methods, using multiparty techniques, or incorporating error-correcting code strategies. These multiple layers of protection make it extremely difficult to compromise blockchain systems, whose security is highly dependent on the standards and protocols employed.
The developer community is working tirelessly to ensure that these systems are “quantum-proof” and that data remain safe from potential quantum attacks.
It is worth highlighting pioneering initiatives in this area. QAN Platform is building a quantum resistant blockchain from the ground up, while the Quantum-Resistant Ledger (QRL) has already successfully integrated post-quantum algorithms into its operational ecosystem.
Not only innovative startups, but also industry giants like IBM and JP Morgan have launched research projects aimed at incorporating quantum principles into their global financial systems, signalling how strategic this technology has become even for traditional institutions. For this reason, several blockchain projects are already experimenting with quantum-resistant solutions, exploring the integration of post-quantum algorithms to ensure long-term security.
Quantum cryptocurrencies
Quantum innovation is beginning to deeply transform the world of cryptocurrencies, impacting not only the security of blockchains, but also the fundamental mechanisms that govern consensus within decentralized networks. One of the most promising examples comes from the startup BTQ, which has proposed a radical alternative to the traditional Proof of Work (PoW) mechanism currently used by Bitcoin and many other cryptocurrencies.
Proof of Work is the consensus mechanism that enables blockchains like Bitcoin to operate securely without a central authority. It validates transactions and creates new blocks, preventing attacks and manipulation of the network. In PoW, miners compete to solve a complex mathematical puzzle. They must find a special number, called a nonce, which, when combined with transaction data and passed through a hash function, produces a result with a specific number of leading zeros.
This nonce is crucial because it makes block creation computationally difficult, requiring vast amounts of processing power. Anyone trying to tamper with a past transaction would need to redo the mining of that block and all subsequent ones, making such an attack economically unfeasible.
Since there’s no shortcut, miners must try billions of combinations at random. Those with more computational power have a better chance of solving the puzzle first and earning the cryptocurrency reward. Although secure, this system consumes as much energy as entire nations.
CGBS (Coarse-Grained Boson Sampling), proposed by BTQ, instead leverages the properties of quantum physics by using photons that traverse a network of optical paths. Thanks to quantum superposition, each photon explores all possible routes simultaneously, creating complex interference patterns.
The result that emerges naturally from this process is extremely difficult for a classical computer to compute but is generated quickly by the quantum system with energy efficiency potentially a thousand times greater. While PoW relies on brute computational force with thousands of computers attempting solutions in series, CGBS exploits the natural properties of quantum physics to achieve similar results with drastically lower energy consumption. CGBS could represent a sustainable future for cryptocurrencies, preserving security while eliminating their massive environmental footprint.
But research doesn’t stop there. Some scientists are exploring even more visionary concepts, such as quantum coins, digital currencies based directly on the principles of quantum mechanics. These coins would be theoretically unclonable due to the quantum no-cloning theorem, a fundamental law of quantum physics.
In practice, a quantum coin would exist in a unique, non-replicable state, elegantly solving the problem of double-spending without relying on complex consensus algorithms. Interestingly, the idea of quantum coins dates back to the 1980s, long before the invention of Bitcoin. It was proposed by physicist Stephen Wiesner, who imagined a quantum banknote that could not be counterfeited.
Even the process of cryptocurrency extraction, known as mining, could be radically transformed by quantum mechanics. Research institutions such as the Singapore University of Technology and Design are developing quantum mining protocols that leverage the unique properties of quantum systems, such as superposition and entanglement, to perform cryptographic operations far more efficiently than traditional methods.
In practice, instead of relying on long, sequential computations performed by high-powered machines, as is the case in today’s large-scale mining farms, quantum mining could allow much lighter devices, such as future laptops or smartphones, to contribute to the network through parallel and ultra-efficient quantum computations. The result would be a more distributed, accessible, and eco-friendly mining system, in stark contrast to the current centralised and energy-intensive model.
The adoption of these technologies is not a simple path; it will require time, substantial investment, and a profound transformation of existing infrastructure. The specialised quantum hardware needed to implement systems like CGBS is still in experimental development, with prohibitive costs and significant technical limitations. It is therefore a revolutionary vision that, while promising, will likely require years of research, development, and testing before reaching commercial maturity.
Conclusion
The future of cryptocurrencies presents two tightly intertwined challenges. On one hand, is the need to protect them from the threats posed by quantum computers; on the other, the urgency of reducing their environmental impact, which is currently unsustainable in the long run.
Quantum computing, if properly integrated, could offer elegant solutions to both problems, paving the way for cryptographic systems that are more secure, faster, and dramatically more energy efficient. There is a fascinating paradox at the heart of this transformation – the very quantum technology that threatens to undermine the reliability of traditional blockchains might also become the key to reinventing them. A threat that, if understood and harnessed, can be turned into an opportunity, ushering in a new era of resilient and sustainable digital infrastructure.
In this race against time, continued investment in advanced cryptographic research and the experimentation with new computational paradigms will be essential. The goal will not just be to keep up with the growing power of quantum processors, but to do so without compromising the two pillars upon which the future of the digital economy rests – security and sustainability.
As Proof of Work, quantum blockchains, and other technologies evolve to meet the challenges posed by quantum computing, the real leap will also be cultural. The adoption of these tools will not depend solely on their ability to solve complex mathematical problems, but on our capacity to understand them, regulate them, and integrate them responsibly into society.
The quantum revolution will not be just a technological shift. It will offer an opportunity to reconsider how we interact with technology, and serve as a testing ground for our imagination, our foresight, and our ability to govern change.